According to a report published on the FAO’s official website on Tuesday, fighting has led to extensive crop and livestock losses and destroyed greenhouses, veterinary clinics, irrigation systems, tractors and other assets.

Providing a comprehensive assessment of the war's impact on agriculture, the report further said food production dropped to an all-time low last year, with many farmers forced to abandon their land.

Those remaining urgently need basic supplies like fertilizer, seeds and medicines for livestock in order to revamp production, but funds are scarce, the FAO said.

The assessment included surveys of more than 3 500 households across Syria, interviews with more than 380 community groups and analysis of primary and secondary agricultural data.

"Ramping up investment in the recovery of the agriculture sector could dramatically reduce the need for humanitarian aid," FAO Director-General Jose Graziano da Silva said in a statement.

"It could also have a significant impact on stemming the flow of migrants."

Rebuilding the agricultural sector would cost between $10.7 and $17.1 billion over the first three years, depending on how the conflict develops, the report said.

The analysis, based on surveys last September of more than 3,500 households across the country, found that Syria's rural population had more than halved since 2011.

Nine in 10 families now spend more than half their income on food, up from 25 percent before the war, due to soaring food prices and the decline in farming income, it said.

More than 7 million people in Syria are classified as "food insecure", meaning they are not always sure where their next meal is coming from, according to the FAO.

FAO says, since 2011, it has supported the livelihoods and food and nutrition security of more than 2.4 million Syrians in rural and peri-urban areas of Aleppo, Al-Hassakeh, Dara'a, Deir-ez-Zor, Hama, Homs, Idlib, Rural Damascus, Sweida and Quinetra.

Over the past almost six years, Syria has been fighting foreign-sponsored militancy. UN Special Envoy for Syria Staffan de Mistura estimated in August that more than 400,000 people had been killed in the Syrian crisis until then. The UN has stopped its official casualty count in Syria, citing its inability to verify the figures it receives from various sources.

More than 11 million, about half the population, are also displaced either internally or as refugees.